All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The criterion for accepting or rejecting the marriage proposal of this suitor should be his religiosity and manners. If he is religious and well-mannered, you should accept his proposal. It was authentically reported on the authority of Abu Hurayrah that the Prophet, sallallaahu ‘alayhi wa sallam, said, "If there comes to you one with whose character and religious commitment you are pleased, then give (your daughter or female under your care) to him in marriage, for if you do not do that there will be Fitnah (temptation/tribulation) in the land and widespread corruption." [At-Tirmithi and Ibn Maajah]
There is no harm in what he said as long as he is religiously committed, as a religious person may be ignorant of the prohibition of celebrating Christmas, and then when he is informed of the prohibition, his religious commitment will urge him to refrain from celebrating it.
However, if the religiosity and manners of this suitor are not pleasing, then we advise you to not accept him as a husband.
Allah knows best.